Final answer:
The tropical rainforest biome has the greatest diversity of species. Hence option D is correct.
Step-by-step explanation:
Tropical rainforests are known for having the greatest diversity of species among the listed options. These ecosystems, characterized by high temperatures and abundant rainfall throughout the year, provide a variety of niches and habitats that support a wide array of plant and animal life. The complex structure of the rainforest, with multiple layers of vegetation, creates diverse microenvironments that contribute to the richness of species.
Aquatic biomes, while diverse, can vary widely in species richness depending on factors such as the type of aquatic environment (marine or freshwater) and the specific ecological conditions. Grasslands and deserts, while important ecosystems, typically have lower species diversity compared to tropical rainforests. Hence option D is correct.